Cooling off of sand and gravel



Feb. 12, 1952 J. D. CHRISTIAN 2,585,739

COOLING OFF OF SAND AND GRAVELS Filed March 29, 1950 SAND /6 PEA GEAVELBLENDER 8 HEAT Emu/V055 9 sc/zEE/v /0 COLD SAND 6040 /Z PEA 6 64 VELSAND /6 7- PEA GPAVEL 4 HEA T L'XCHA Nam BLENDEE 5 sclzEE/v m COL D COLD.548 g PEA 612A VEL INVENTOR. (105.52% 0. CHRIS T/AN A TTOQNE Y PatentedFeb. 12, 1952 UN lT-ED. STATES PATENT 4 Claims.

This invention relates to the preparation of pea gravel and sand for usein the manufacture of large, massive structures of concrete.

It has long been recognized that large concrete structures, such asdams, are subject "to cracking if the temperature of the mass increasesappreciably during setting of the cement. To ensure this will not occur,various steps have been takensuch as actual inclusion in the structuresof conduits for circulation of cooling fluids. In addition, the coolingof the coarse aggregate utilized in such concrete structures has longbeen practiced; coarse aggregate comprises the rock from 6" to size.Suchcoarse material can be cooled by flooding with cold water and thendraining, or by circulating cold air over the rock mass. Concrete,however, in addition to the aforementioned aggregate, includes peagravel, and, cement and water. It has not been feasible to cool the peagravel and sand heretofore inasmuch as each offers too great aresistance to the flow of the air while inundation with cold water isnot suitable inasmuch as the pea gravel must be drained to enableadequate moisture control to be maintained and the water properlyproportioned in the resulting mix. When inundation is attempted upon peagravel, by the time the pea gravel has drained adequately, it will haveattained a normal atmospheric temperature so that the efiect of coolingis completely lost. Similarly, inundation with cold water is impracticalupon sand, the inundation floating on too many of the fines from thesand; in addition, it must be drained.

I have found that the pea gravel and sand can be suitably cooled bymixing the two together, cooling the resulting mass by indirect contactwith a refrigerating or cooling fluid and subsequently separating thetwo materials so that they can later be accurately proportioned for theconcrete mix. It is not necessary initially to mix the pea gravel andsand and one can utilize instead a natural material or even artificallyproduced but which can be subsequently sized to provide the pea graveland sand components. Pea gravel as such cannot be cooled efficientlybecause of its granular nature which provides a considerable volume ofvoids. By adding said to the pea gravel, the voids are filled andefiicient cooling achieved.

It is in general the broad object of the present invention to provide anovel method of cooling pea gravel and sand for use as in concretemanufacture.

Another object of the present invention is to provide a novel apparatusfor cooling oi -pea gravel and sand.

The invention includes other objects andfeatures of advantage, some ofwhich, together with the foregoing, will appear hereinafter wherein thepresent preferred form of method and 3p.- paratus embodying thisinvention are disclosed.

In the drawings accompanying and-forming a part hereof, Figure 1andFigure 2 are, respectively,-diagrammatic illustrations of apparatusand process steps utilized in practicing the present invention.

Referring particularly-to Figure 1, Ihave indicated a stock pile ofsandt and a stock pile of pea gravel I as sources of suitable materials.These are delivered'continuously and at a sub! stantially uniform rateinto a blender ormixer 8, the latter being preferablycooled. Thereafter,the resulting homogeneous-mixtureof. pea gravel and sand is passedthrough a cooler gen-1 erally indicated at 9 such as the heatexchangescrew conveyor structure disclosed in my Patent 2,321,185; onecan also utilize other structures such as one wherein two or more ofsuch heatexchange conveyors are provided rotating in opposite directionsin a suitable casing which is also cooled, the flights rotating aboutparallel axes with the flight on one in almost wiping contact with thesupporting hollow shaft of the other,

flight. One can also use four or six such flights arranged in aside-by-side relation with any two adjoining flights in such near-wipingcontact. Such flights can be utilized in tiers to provide the heatabstraction required.

From the cooler 9, the cooled mass is delivered to a screen I0 whereonit is separated into sand and pea gravel, these being delivered to thestock piles II and I2.

In Figure 2, I have illustrated another form of practicing the inventionwherein sand and pea gravel from the stock piles 6 and 1 are utilized.However, in this case, the sand from stock pile 6 is passed through apreliminary cooler I4 wherein it is separately cooled and after which itis passed to the blender 8, to which the pea gravel is also deliveredfrom stock pile I. The mixture from the blender 8 is then passed throughthe cooler 9 and thereafter the cooled mixture is passed over screen IDto separate the pea gravel from the sand.

By mixing the pea gravel and sand, the voids in the pea gravel arefilled adequately so that an .efilcient cooling is practical upon thepea gravel whereby the mixture is cooled rapidly and effectively. Inaddition, attrition which occurs upon the pea gravel during the severalsteps does not affect the quality of the pea gravel adversely inasmuchas any fines created and which are suitable for inclusion in the coldpea gravel fraction are included in the cold sand fraction; pea gravelis defined herein and in the claims as generally including that materialpassing a mesh screen and which is retained upon a 4 mesh screen, whilesand is defined herein and in the claims as generally'including thatmaterial passing a 4 mesh screen and which is usually all retained on a100 mesh screen.

In a typical operating example, pea gravel and sand were utilized, thetemperature of each being 92 F. The sand was passed through a firstcooler l4 wherein it was cooled at 6 F., thereafter being mixed with the92 F. pea gravel in blender 8 wherein the mass was further cooled withthe result that the temperature of the material issuing from the blenderwas 65 F. Thereafter, the homogenous mass was passed through the secondcooler wher-einthe temperature of the mass was lowered to 45" F. The twomaterials were then passed over the screen It) wherein they wereseparated into a cold pea gravel fraction and cold sand fraction, eachready for utilization immediately in the concrete manufacturingoperation.

Sand usually comprises about one-fourth the aggregate volume and peagravel about an eighth. By cooling these, one is about to cool a verysubstantial volume of the solids utilized. The invention is not limitedto sand and pea gravel fractions for the larger aggregate can beincluded as well if this be desired, but not to eX- clusion of the sandand. pea gravel fractions.

I claim:

1. A process for pre-cooling concrete constituents comprising mixing apea gravel fraction 4 and a sand fraction to provide a homogeneous mass,cooling said mass to a desired temperature by passing the mass over acooled heat exchange surface, and separating the cold pea gravelfraction from the cold sand fraction.

2. A process for pre-cooling concrete onstituents comprising cooling asand fraction, mixing a pea gravel fraction and the so-cooled sandfraction to provide a homogeneous mass, cooling said mass to a desiredtemperature by passing the mass over a cooled heat exchange surface andseparating the cold pea gravel fraction from the cold sand fraction.

3. In the preparation of concrete fractions, the steps of cooling amass, including a pea gravel fraction and a sand fraction, to a desiredtem- REFERENCES CITED The following references are of record in the-file of this patent:

) UNITED STATES PATENTS Number Name Date 1,304,619 Stamp May 27, 19191,905,602 Patterson Apr. 25, 1933 2,491,194

McShea Dec. 13, 1949

